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LABORATORY GUIDE 
IN MARKET MILK 



ROSS 




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COPYRIGHT DEPOSnV 



LABORATORY GUIDE 

IN 

MARKET MILK 






ErROSS, 

Professor of Dairy Industry, New York Slate College of Agriculture 
at Cornell University 



1915 

CARPENTER & CO. 

ITHACA, N. Y. 






COPYRIGHT 
I915 

Carpenter & Co. 



s^^c?: 



r« 



PRESS OF \V. F. HUMPHREY, GENEVA, N. Y. 



©CI,A416655 

DEC -I 1915 



PREFACE 

The production and handling of clean milk is based on scientific 
principles. It is true that many of these principles are simple in their 
^application and oftentimes on account of their simplicity they are 
overlooked and neglected. It is the purpose of this laboratory guide 
to enable the student to better understand the application of science 
to clean milk production, and to impress on his mind the necessity for 
attention to detail in this branch of Dairy Industry. 

Our ideas concerning the best methods of clean milk production 
are constantly changing. The Author recognizes that this will 
necessitate frequent revision of this book and an effort will be made to 
keep this laboratory guide thoroughly up-to-date. 

H. E. Ross. 

Dairy Laboratories 

New York State College of Agriculture 

at Cornell University 

Sept. 14, 1915 



It is generally accepted that clean milk means milk which is free 
from microorganisms or the products of their action. It is possible 
to conceive of milk being impure from something other than micro- 
organisms or their products, such as the addition of some poisonous 
substance to milk. The possibility of such contamination is, however, 
so rare and so remote that the words "imptire milk," have come to 
mean that which is affected by the action of microorganisms. 

For this reason all operations and experiments performed in a 
laboratory should be done in such a way as to prevent bacterial con- 
tamination, and all dairy utensils with which the milk comes in con- 
tact should be rendered sterile so far as possible. This can be done 
by thoroughly scalding all dairy apparatus, or better still by 
exposing them to live steam for not less than one hour. If the 
dairy utensils are scalded by means of hot water, the temperature of 
the water should be not less than i8o°F. and it should be as near the 
boiling point as possible. 

Dippers and other dairy utensils in which milk is handled, or which 
comes in contact with the milk in any way, should not be laid on the 
floor and then placed in the milk. Care should be taken not to touch 
the surfaces of dairy utensils, such as coolers, bottle fillers and so 
forth, with the hands. Water even in small amounts, may, if allowed 
to enter milk, cause it to putrefy. 

Cleaning Dairy Utensils 

Dairy utensils must be thoroughly cleaned if milk is to be handled 
in a sanitary manner. The proper way in which to clean a dairy 
utensil is to first rinse it with cold or luke-warm water, preferably the 
latter. This removes most of the milk from the utensil and prevents 
later cooking of the albimien of the milk on to the apparatus, when it 
is scalded or sterilized. The utensil should next be thoroughly washed 
by means of a brush and hot water in which there has been dissolved 
some good washing powder. An excessive amount of powder is not 
necessary, a tablespoonful to a pail of hot water is usually sufficient. 
The utensil should then be scalded in hot water, and if possible, 
exposed to the action of live steam for not less than one hour, thereby 
rendering the utensil as sterile as possible. It should be kept in a 
place where it will not become recontaminated. 

5 



EXPLANATION OF EXERCISE I 

In studying any dairy utensil, it should be noted whether the uten- 
sil is so arranged and constructed as to best fulfill the purpose for 
which it is intended. All dairy utensils should be as simple as possible 
in construction. They shovild have no seams and crevices into 
which milk can collect. Any cracks or seams in copper or tin 
surfaces should be well flushed with solder. AH parts should be 
accessible so that they may be thoroughly cleaned. They should 
be strong and durable and at the same time, any extra metal or other 
material is objectionable. On account of its durability and the ease 
with which it may be cleaned, metallic is usually preferable to wooden 
construction. 

When possible, metallic construction should be of some non-rusta- 
ble material. 

EXERCISE I 
A Study of Dairy Apparatus 

1. Bottle Fillers — Study the tubes of the different fillers used. 
Show by drawings how the milk flows from the tank through the tube 
into the bottle, and the provision made for removing air and surplus 
milk from the bottle. 

Pasteurizers — Show by cross-sectional drawing the method of 
operation of a holder pasteurizer and a flash pasteiuizer. 

2. Clarifiers — Explain the action of a centrifugal clarifier. In 
each case show by means of a drawing the chief differences between 
the inner device of the clarifier and a cream separator of the same 
make. Also compare the relative speed of clarifiers and separators 
of the same make and having the same capacity per hour. 

3. Coolers — Make drawings of a conical and tubular type of 
cooler and explain the action of each. 

In case of the tubular cooler, show its connection with a brine 
barrel and indicate the relative position of the cooler, brine barrel and 
pump. 

4. Milk Bottles — Make drawings of two different styles of milk 
bottles. 



7 

STUDENT'S NOTES AND REPORT 



DIRECTIONS FOR STANDARDIZATION 

The process of standardization consists in raising or lowering the 
percentage of fat in milk or cream to a definite standard. This is 
done by adding milk of a higher or lower fat content, than the material 
which is being standardized. 

Some market milk does not normally contain sufficient fat to be 
satisfactory to the consimier. In order to make this milk satisfactory 
the dealer oftentimes standardizes it by the addition of cream. 

Since the law states that unadvdterated milk is milk to which 
nothing has been added or anything taken aw&,y, there has been 
raised some slight question as to the legality of the process of stand- 
ardization. However, the addition of cream to milk increases its 
value, so that no serious objection has been raised to that part of the 
process. One would, however, have no right to reduce the fat con- 
tent of milk by the addition of skimmed milk, as this would be 
essentially the same as removing fat from the milk. 

At the present time much of the cream sold is paid for on a basis 
of its fat content and for this reason a knowledge of standardization is 
useful to the cream shipper. If a dealer receives a certain price for 
cream containing a definite percentage of fat it is desirable to have no 
more or no less fat than the percentage agreed upon. If there is more 
fat than the contract calls for, the seller loses, and if there is less fat 
the buyer loses. 

In standardization there are two classes of problems involved: 
first, one in which two products containing a known percentage of fat 
are mixed to make a definite amount of milk or cream containing a 
fixed percentage of- fat, and second, one in which a definite amount of 
milk or cream of a known percentage of fat is used and enough of some 
other product added to make the resulting mixture test the desired 
percentage of fat. In the first case the amount is definite, and in the 
second case it is indefinite. 

The usual method of working standardization problems is quite 
difficult, but Pearson has devised a method which greatly simplifies 
the computation. It is as follows: Draw a rectangle and place in 
the center of it the percentage of fat desired. On the left hand 
comers place the percentages of fat in the materials to be mixed. It 
is customary to place the larger percentage on the upper left hand 
corner and the smaller percentage on the lower left hand comer, 

8 



although the position of these numbers might be reversed without 
affecting the results. Subtract the smaller number on the left hand 
comer of the rectangle from the number in the center and place the 
remainder on the diagonally opposite right hand comer. Then sub- 
tract the number in the center of the rectangle from the larger number 
on the left hand comer and place the remainder on the diagonally 
opposite right hand comer. The two mmibers on the right hand 
comers of the rectangle represent the mmiber of potmds of materials 
required. The sum of these two numbers will be a mixtiu"e containing 
the desired percentage of fat, expressed by the number in the center 
of the rectangle. 

In each case the nimiber on the right hand comer of the rectangle 
corresponds to the number on the left hand comer directly opposite. 

A few concrete examples will illustrate the rectangle method of 
working problems in standardization. 

Problem I. How many pounds of 23% cream and 3% milk will be 
required to make 500 pounds of an 18% cream? Using our diagram 
as described above we have the following results: 



These results mean that if five povmds of 3% milk were mixed with 
IS poimds of 23% cream the result will be 20 pounds of a mixture 
testing 18%. The amount of the mixture desired was 500 pounds, 
which is twenty-five times the amount obtained with the rectangle 
method (500 -^ 20 = 25). If we multiply the numbers on the upper 
and lower right hand comers of the rectangle by twenty-five we will 
obtain respectively the pounds of 23% cream and 3% milk required 
to make 500 pounds of an 18% mixture. These are 375 potmds of 
23% cream (15 x 25 = 375), and 125 pounds of 3% milk (5x25 = 
125). 

The problem may also be worked by simple proportion : 
5:20 :: X : 500 

20X = 2500 
X = 1 2 5 pounds of 3 % milk. 
15:20 :: X 500 

20X = 7500 
X = 375 pounds of 23% cream. 



lO 

In the above problems the amount of the mixture desired is 
definite. 

In working problems in standardization it is wisest to prove the 
answer as this will show if the results are correct. While proving 
a problem will point out errors it will not show where mistakes have 
been made. The proof of the above problem is as follows: 

Proof: 

It is desired to make 500 pounds of an 18% mixture which would 
necessarily contain 90 pounds of fat (500 X .18 = 90). According to 
our computations the 500 pounds of 18% cream will consist of 125 
pounds of 3% milk and 375 pounds of 23% cream. If these materials 
furnish 90 pounds of fat, the problem is worked correctly. One 
hundred twenty-five pounds of 3% milk will contain 3.75 pounds of 
fat: (1.25 X .03 = 3.75). Three hundred seventy-five pounds of 
23% cream will contain 86.25 pounds of fat (375 X .23 = 86.25), 
86.25 -f- 3.75 = 90 pounds of fat. 

In the following problem the amount of mixture to be made up 
is indefinite. 

Problem 2 : 

How much 23% cream must be mixed with 500 pounds of 3% milk 
to make a mixture testing 1 8% ? Using our diagram according to the 
directions previously given we have the following results: 



These results mean that we must mix the materials in the proportion 
of 15 pounds of 23% cream to five pounds of 3% milk to make an 
18% mixture. According to the conditions of the problem we must 
use 500 pounds of 3% milk which is 100 times as large as the amount 
given in the above proportion (500 -^ 5 = 100). The 23% cream and 
the 3% milk must be kept in the proportion of 15:5 and if the 3% 
milk is increased one hundred times the 23% cream must be increased 
the same number of times. This would give 1500 pounds of 23% 
cream (15 X 100 = 1500), which should be added to the 500 pounds 
of 3% milk, giving 2000 pounds of an 18% mixture. The problem 
may also be worked by simple proportion. 



II 

15 : 5 :: X : 5°° 
5X = 7500 

X = 1 500 pounds of 23% cream. 
Proof: 

The 2000 pounds of 18% cream will contain 360 pounds of fat 
(2000 X .18 = 360). According to our results, the 2000 pounds of 
18% cream is made up of 500 pounds of 3% milk a!nd 1500 pounds of 
23% cream. The 500 pounds of 3% milk will contain 15 pounds of 
fat (500 X .03 = 15). The 1500 pounds of 23% cream will contain 
345 pounds of fat, 345 + 15 = 360 pounds of fat, which is the number 
of pounds in the mixture. 

In the original method of working problems in standardization all 
computations are made on a pound basis. From this basis it is easy 
to compute the amount of different materials needed to make up any- 
given quantities of milk or cream. Problems are worked by this 
method as follows: 
Problem 3. 

How much 23% cream must be mixed with 500 pounds of 3% milk 
to make a mixture testing 18% ? 

One pound of 23% cream will contain .23 pounds of fat. 
One pound of 3 % milk will contain .03 pounds of fat. 

The difference is 20 pounds of fat. 

Every time one pound of .23% cream is removed and a pound of 
3% milk substituted there is removed .20 pounds of fat. 
One pound of 23% cream contains .23 pounds of fat. 
One pound of 18% cream contains .18 pounds of fat. 

The difference is 05 pounds of fat. 

It is desired to reduce the fat content .05 pounds of fat for ever^'- 
pound of the mixture. This is done by the addition of 3% milk 
which may in this case be regarded as a reducing agent. Since the 
substitution of a pound of 3% milk for a pound of 23% cream reduces 
the fat content of a pound mixture .20 pounds of fat and it is desired 
to reduce the fat content .05 pounds of fat, it will require as much 
of the 3% milk as .20 is contained into .05 or .25 (.05 -^ .20 = 25). 
The .25 is the number of pounds of 3% milk there would be in one 
poundof an 18% mixture. The remainder . 7 5 pounds ( i — -25 = .75), 
would be 23% cream. The following simple proportion will gi^^e the 
nxmiber of pounds of 23% cream which must be added to 500 pounds 
of 3% milk to make a mixture testing 18% fat. 



12 

•75 "25 : : X : 500 
•25 X = 375 
X = 1 500 pounds of 23% cream. 

The following problem is an illustration of the original method 
of working standardization problems when a definite amount of the 
mixture is desired. 

Problem 4. 

How much 23% cream and 3% milk must be mixed to make a 
cream testing i8%? Since the percentages of fat in these problems 
are the same as those in Problem 3, the amount of 3% milk in one 
pound of an 18% mixture woiild be the same as already shown, and 
therefore needs no further explanation. Since .25 is the number of 
pounds of 3% milk in one pound of 18% cream, we would have the 
simple proportion: 
i:.2S :: 500 : X 

X = 125, the nimiber of pounds of 3% milk in an 18% mixture. 
The remainder of the mixture, 375 pounds (500 — 125), will be 23% 
cream. The cream could, of course, be found by forming the follow- 
ing simple proportion. 
i:.75 :: 500 : X 

X = 375 pounds of 23% cream. 

Note: — In the two following exercises on Standardization it is 
intended that one shall consist of a problem where the amount to 
be standardized is definite and the other shall be a problem where the 
resulting amount is indefinite. 



EXERCISE II 

Standardizing 

I. Test for fat by the Babcock method the samples of milk and 

cream to be used in standardization. Report the percentages of 

fat found and a definite percentage to which the milk or cream is to 

be standardized will be assigned. 

2 After standardizing the milk or cream as directed, test it for 
fat by the Babcock method in order to verify the accuracy of yDur 
work. 



13 
STUDENT'S NOTES AND REPORT 



14 

EXERCISE III 

1 . Test for fat by the Babcock method, the samples of milk and 
cream to be used in standardization. Report the percentages of fat 
found and a definite percentage to which the milk or cream is to be 
standardized will be assigned. 

2. After standardizing the milk or cream as directed, test it for 
fat by the Babcock method in order to verify the accuracy of your 
work. 



15 
STUDENT'S NOTES AND REPORT 



PASTEURIZATION 

Pasteurization applied to dairy work is the process of heating milk 
or cream to a temperature sufficiently high and for a time sufficiently 
long to kill most of the organisms in them. The materials should 
then be cooled to a temperature of 50 F. or lower to prevent germ 
growth. Cooling the product is just as important a part of the 
process as is heating, for if there are any organisms not killed by the 
heating process, they will multiply rapidly if the milk or cream is kept 
at temperatures favorable for germ growth. Milk or cream from 
the market standpoint should be kept at just as low a temperature as 
possible and still not freeze them. 

Pasteurization has for its purpose two objects, (i) the killing of 
pathogenic- organisms, and (2) checking germ growth. The first is 
the most important, and it is supposed that the process of pasteuriza- 
tion is efficient in destroying all pathogenic organisms. This supposi- 
tion is based upon a great many experiments on the thermal death 
point of such pathogenic organisms as those which cause tuberculosis, 
typhoid, and diphtheria. 

Pasteurization differs from sterilization in that the latter process 
kills all living material in and about an object. It is not possible to 
sterilize milk for market purposes because the high temperatures and 
length of time required for sterilization change the normal taste of 
milk and render it objectionable to the consumer. Too high tempera- 
tures also change the chemical composition of milk, the chief of these 
changes being the precipitation of albumin and causing the lime salts 
to become more insoluble. For these reasons both the degree of heat 
and the length of time employed in the process of pasteurization are 
limited. 

There are two methods of pasteurization one called the flash 
method and the other the holder method. In the flash method, milk 
is heated to a comparatively high temperature for a short time, 
usually 160° F. for one minute or less, and frequently the time which 
the milk is subjected to the proper temperature is only a few seconds. 

In the holder method, milk is heated to a low temperature for a 
comparatively long period of time, 140° F. — 145° F. for 30 minutes 
being a very common time and temperatiire employed. The holder 
process of pasteurization is considered more efficient than the flash 

16 



17 

method and many boards of health have forbidden the use of the flash 
method of pasteurization of milk sold under their jurisdiction. 

Pasteurization should never be used as a means of placing dirty 
milk upon the market. While the process does kill the micro- 
organisms found in milk it does not always destroy their products, 
and if badly contaminated milk is pasteurized and placed upon the 
market, although its germ content may be small, it may still be unfit 
for human consumption. 

EXERCISE IV 

Pasteurization by the Holder Method 

Note: — This exercise should be performed in combination with 
Exercise V. 

1 . Thoroughly mix four cans of milk by pouring from one can to 
another. Take in a sterile bottle a small amount of milk from each 
can and place the sample on ice until it can be plated for bacteria. 
Two of the cans of milk are to be used in Exercise V. 

2. Thoroughly scald the machine. This may be done by running 
hot water through the coils. Pasteurize two cans of milk at a tem- 
perature of 140 F. for 30 minutes. After heating the milk for the 
proper time at the proper temperature, cool the milk to as low a 
temperature as possible in the time allowed and lower the temperatiire 
of the milk as rapidly as possible. Carefully record the weights of 
the milk used, the time required to raise the milk to 140° P., the 
temperature to which the milk was cooled, the temperature of the 
refrigerating substance as it enters the coils, and the time required for 
the entire process. 

When the process is complete, take in a sterile bottle a sample 
of the milk to be plated for bacteria. Compare the bacteria counts 
obtained with that of the raw milk, and that from the milk pas- 
teiuized by the flash method. 



i8 

STUDENT'S NOTES AND REPORT 



EXERCISE V 

Pasteurization by the Flash Method 

Note: — This exercise should be performed in combination with 
Exercise IV. 

1. Thoroughly scald the machine. This may best be done by 
allowing water to pass through the machine and turning on the steam 
at the same time. Allow this hot water to pass over the cooler and 
so far as possible sterilize it. Use for this experiment the two cans 
of milk, mixed as directed in Exercise IV. Pasteurize the milk at a 
temperature of i6o° F. Carefully record the pounds of milk used, 
time required for the process, temperature of refrigerating material 
as it enters and leaves the cooler and the temperature to which the 
milk is cooled. 

2. Take in a sterile bottle a sample of the milk to be plated for 
bacteria. Compare the count obtained with that of the raw milk 
and that obtained from the milk pasteurized by the holder method. 



19 



STUDENT'S NOTES AND REPORT 



21 

EXPLANATION OF EXERCISE VI 

On the average dairy farm, one of the most practical methods of 
cooling milk is to set the can containing the milk in a tank of ice water. 
For this purpose a cement tank is the most durable and in the long run 
cheapest. The walls of the tank should be from foiu- to six inches 
thick and that side on which the milk is lifted in and out of the tank 
should be faced with iron to prevent the cans from chipping the 
cement. The tank will be most convenient if it is sunk in the floor 
as this will make it easier to lift the cans in and out. The walls 
should, however, extend about twelve inches above the floor to pre- 
vent dirt working into the tank. An outlet should be made in the 
bottom of the tank so that it may be easily cleaned as more or less 
milk will be spilled, causing the tank to become unsanitary. 

A galvanized iron tank, useful in cooling milk and capable of hold- 
ing four cans, may be purchased from dairy supply houses for from 
eight to ten dollars. 

In order to have milk cool properly in a tank of this kind it is 
necessary to frequently stir the milk in the cans. Unless milk is 
stirred frequently it will not cool jrapidly and rapid cooling is essential 
in preventing an increase of germ life. 

The purpose of the following exercise is to show the effect of stirring 
at different intervals on the rapidity with which milk cools. The 
student shoiild also draw conclusions regarding the frequency with 
which milk should be stirred to get the best practical results. 

EXERCISE VI 
Cooling Milk in Cans 

1. Heat four cans of milk to 95° F. and place in a tank of ice 
water. For this experiment about 135 poimds of ice will be required. 

Stir can No. I every five minutes and record the temperature. 

Stir can No. II every ten minutes and record the temperature. 

Stir can No. Ill continuously and record the temperature every 
ten minutes. 

Do not stir can No. IV at aU but record the temperature of the 
milk in the center at ten minute intervals. 

2. Carry on the experiment for one hour and at the end of one 
hour thoroughly stir can No. IV and record the temperature of the 
mixed mUk with that of the temperature of the milk before the 
milk was thoroughly stirred. 

3 . Compare the temperature obtained in the four different cans. 
Draw conclusions concerning the frequency with which milk should 
be stirred, to get the best practical results. 



22 

STUDENT'S NOTES AND REPORT 



23 

EXPLANATION OF EXERCISE VII 
There are several kinds of conical coolers on the market, which are 
suitable for use on farms. These coolers furnish an efficient piece 
of apparatus at a reasonable price. Their use has often been abused 
since they are frequently stationed and used in places where they are 
exposed to dust and dirt, and in order to minimize the danger from 
such contamination, some coolers are provided with a hood which 
surrounds that part of the cooler over which the milk flows. The 
refrigerating material most commonly used in these coolers is ice and 
water, although they may be attached to a brine barrel or a running 
water supply, if such a supply is available. Whatever the refrigerating 
substance used in these coolers, it should be stirred frequently. If it 
is not stirred, the refrigerating material next to the walls soon becomes 
warmed by the milk passing over the cooler and so loses its efficiency. 
The purpose of the following experiment is to compare the effi- 
ciency of a conical type of cooler when the refrigerating material 
inside the cooler is stirred and when it is not stirred. 

EXERCISE VII 
Cooling Milk with a Conical Cooler 

1 . Weigh a can of whole milk and heat it to 95° F. The purpose 
of heating the milk is to bring it to nearly the same temperature as 
when drawn from the cow. Place forty pounds of ice inside the cooler 
and fill the cooler to the overflow pipe with cold water. Run the 
milk over the cooler and note the time it takes the first milk which 
comes from the receiving tank to reach the outlet spout of the cooler. 
Do not stir the water inside the cooler. Record the temperature of 
the milk at the outlet spout every three minutes. Note the time 
required to pass the milk over the cooler. After all of the milk has 
passed over the cooler, stir it thoroughly and record the final tempera- 
ture. Take the temperature of the water near the walls of the cooler. 
Stir the water and then take its temperature. Weigh the amount of 
ice left. 

2. Repeat the experiment, heating the milk to the same tempera- 
ture and using the same amount of ice, but in this case stir the ice 
water in the cooler continuously. Record the temperature of the 
milk every three minutes. Stir the can of milk and take the final 
temperature. Weigh the amount of ice left. Compare the results 
obtained by the two methods of cooling. Make a drawing of the 
cooler. Compute the capacity of the cooler per hour. 

State in your notes the name of the cooler used. 



24 

STUDENT'S NOTES AND REPORT 



COMPUTING AMOUNT OF ICE NECESSARY TO COOL A 
GIVEN AMOUNT OF MILK 

The study of refrigeration is essentially a study of heat. The unit 
of heat used by refrigeration engineers is called the British Thermal 
Unit, and it is the amount of heat reqmred to raise one pound of water 
one degree Fahrenheit at its maximum density, 39.1 F. 

Not all substances require the same amount of heat to raise their 
temperattue per unit of mass. Water is taken as a standard, and the 
ability of a substance to absorb heat in comparison with water is 
called the specific heat of the substance. The specific heat of water 
is called i , and most substances have a specific heat less than that of 
water. The specific heat of milk is variable, depending to a large 
extent upon the temperature and the variation in fat content. The 
lower the fat content the higher the specific heat. The specific heat 
of normal milk is variously given by different investigators as ranging 
between .92 and .95. In computations on refrigeration, the melting 
point of ice is used as a basis, because this is definite and constant. It 
requires 144 B. T. U. to melt one pound of ice, and knowing this fact, 
the amount of ice necessary to cool a given amount of milk may be 
readily computed. The method of computation may best be illus- 
trated by a specific problem. 

How many pounds of ice will be required to cool 500 pounds of 
milk from 80° F. to 32° F. ? In this case, the specific heat of the milk 
is considered as .93. 

Five hundred X .93 = 465, the number of heat units required 
to raise the 500 pounds of milk one degree as compared with the same 
amount of water. Since the milk is to be cooled 48 F. (80 — 32= 48) 
multiplying 465 by 48 will give 22,320 heat units to be extracted from 
the milk, (465 X 48 = 22,320). Since it requires 144 B. T. U. to 
melt one pound of ice, it would require as many pounds of ice to cool 
the 500 pounds of milk as 144 is contained in 22,320, or 155, (22,320 -^ 
144 = 155). 

If the milk is cooled to a temperature above 32 F. the available 
refrigeration of one pound of ice is increased and the difference 
between 32° F. (the temperature of the melting ice), and the tempera- 
ture to which the milk is cooled, must therefore be added to the 
B. T. U. necessary to melt a pound of ice (144). 



25 



26 

For example, suppose we wished to find the number of pounds 
of ice necessary to cool 500 pounds of milk from 80 F. to 40 F. 
Assuming the specific heat of the milk to be .93, the number of heat 
units to be extracted from the milk would be 500 X .93 X 40 (80 — 40 
= 40) = 18,600. Since the milk is to be cooled to a point 8 F. above 
the melting point of ice (40 — 32 = 8), the available refrigeration of a 
pound of ice would be increased to 152 (144 + 8= 152). The num- 
ber of pounds of ice necessary would therefore be 18,600 -^ 152 = 122.3 
pounds. 

The theoretical amount of ice will usually be insufficient to cool 
milk to the desired temperature. This is because of outside influences 
such as temperature of the air, temperature of the water with which 
the ice is mixed, and temperature of the apparatus through which the 
water is run. 

EXPLANATION OF EXERCISE VIII 

Lower temperatures may be obtained with a mixture of salt and 
ice than with ice alone. This is because of the fact that when two 
solids unite to form a liquid, they absorb heat. Within certain limits 
the larger the percentage of salt used, the lower the temperature that 
can be obtained. After a certain amount of salt has been added the 
solution becomes saturated and the further addition of salt has no 
effect in lowering the temperature. 

The following table from B. A. I. Biilletin No. 98 gives the approxi- 
mate temperatures which may be obtained with different percentages 
of salt and ice. 



Percentage of salt in 
mi.xture 


Temperature of 

mixture 

op 


% 


of salt in 
mixture 


Temperature of salt 

in mixture 

op 





32 




15 


II 


s 


27 




20 


1-5 


10 


20 




25 


-ID 



27 

EXERCISE VIII 
Comparative Efficiency of Ice Water and Brine and Ice 

Use for this experiment a Tubular cooler. 

Heat two cans of milk to 95°F. The piirpose of heating the milk 
to this temperature is to have it nearly the same temperature as when 
drawn from the cow. Weigh the amount of milk used. Weigh out 
about 125 pounds of ice. Crush it and place it in the brine barrel. 
Run in cold water until the barrel is about half full. Stir the mixture 
of ice and water. Allow the pump to run for about two minutes or 
until the temperature of the water in the barrel is 32 F. before run- 
ning the milk over the cooler. Then run the milk over the cooler at 
its full capacity. Record the length of time required to cool the milk 
and take the temperature of the milk at the outlet faucet every three 
minutes. Thoroughly stir the milk in the can and record the final 
temperature. Record the temperature of the return water from the 
cooler every three minutes. Weigh the amount of ice left. 

Repeat the experiment, heating the milk to 95 F. and using the 
same amount of ice. The ice left from the previous experiment 
may be used in this one. Add 40 pounds of salt to the mixture in this 
barrel and thoroughly stir until the salt is dissolved. The amount 
of salt required will depend somewhat on its quality. If it is insoluble, 
more will be required. Have the temperatiu-e at 28 F. to 30 F. 
Take temperature of the milk every three minutes, the temperature 
of the return water every three minutes, and the final temperatiire of 
the milk in the can. Weigh the amount of ice left. Draw diagram 
of the cooler, and figure out its capacity per hour. Show in drawing 
the relative position of the cooler, brine barrel, and pump. 



28 

STUDENT'S NOTES AND REPORT 



29 

EXERCISE IX 

Heat to a temperature of 95° F., two cans of milk. Weigh out 
125 poimds of ice, crush it, and place it in the brine barrel which has 
previously been filled about half full of cold water. Add, in salt, to 
the ice water in the barrel, 5% of the weight of the ice. Thoroughly 
mix the salt and ice water in the barrel and pump the brine through 
the cooler, noting its temperature before starting to cool the milk. 

Cool the milk and take the temperature of the mixed milk after 
cooling. Also take the temperature of the brine as it comes from the 
cooler. Weigh the ice if any is left, and save it for use in the second 
part of the experiment. 

Remove all of the brine from the barrel and flush out the barrel 
and cooler by ptmiping cold water through them. Repeat the above 
experiment using 1 5 % of salt instead of 5 % . Record all temperatures 
the same as in the first part of the experiment. 



30 
STUDENT'S NOTES AND REPORT 



THE DAIRY SCORE CARD 

The dairy score card is a card on which are enumerated the good 
points which a dairy shotild possess, and these points are given 
numerical values. The score card is divided into two distinct 
divisions, equipment and method. Out of a possible loo points for a 
perfect score, 40 are given to equipment and 60 to methods. This 
numerical division is made to give a just recognition to the importance 
of proper methods in the production of clean milk. Good equipment 
should be an aid in clean milk production, and other things being 
equal, a dairyman will produce better milk with good equipment than 
with poor equipment. However, good equipment without proper 
method will not produce wholesome milk. 

Those who use the score card should not regard it as an infallible 
set of rules from which no deviation should ever be made. It is 
simply a guide to help the producer to see the conditions of his dairy 
and to help the inspector to judge intelligently of those conditions. 

The chief value of the score card is that when properly used it is 
educational, and it is educational because it not only points out 
defects, but it emphasizes the seriousness of these defects. In this 
way the dairyman is given a chance to improve in these things which 
will aid most in clean milk production. 



31 



32 

EXPLANATION OF EXERCISES X, XL AND XII 

Score dairies according to the official score card, and place the 
score of the different points on the card. In the blank page reserved 
for notes, write a short criticism of the place scored, and note those 
things which might be done to improve the milk supply, and at the 
same time would not require a big outlay of capital. Also criticise 
the methods employed, in the same way. 

Note : — It is intended that at least three dairies of different grade 
should be scored, one having excellent buildings and equipment, one 
having medium buildings and equipment, and one having poor 
buildings and equipment. It would be desirable if the high grade 
dairy was producing certified milk, or milk of similar grade, and the 
poorly equipped dairy was producing a good grade of milk by means of 
superior methods. This would emphasize the importance of clean 
milk production. If time permits, more than three dairies may be 
scored, as it is highly desirable that all the practice possible be given 
to this part of clean milk production. 

EXERCISE X 
/ Judging Dairy Barns 

1. Score according to the official score card the dairy visited. 
Place the score allowed the different points on the score card. 

2. On the sheet allotted to notes, write a brief criticism of the 
dairy and the methods employed. Pay particular attention to those 
things which are important in clean milk production, and at the same 
time would not require a big outlay of capital. 



STUDENT'S NOTES AND REPORT 

SCORE 



SCORE 



EQUIPMENT 



Perfect Allowed 



cows 

Health 

Apparently in good health i 

If tested with tuberculin within a 

year and no tuberculosis is found, 

or if tested within six months and 

all reacting animals removed . . . . s 

If tested within a year and reacting 

animals are found and removed 3 

Food clean and wholesome 

Water, clean and fresh 

STABLES 

Location of stable 

Well drained I 

Free from contaminating surround- 
ings I 

Construction of stable 

Tight, sound floor and proper gutter2 
Smooth, tight walls and ceiling . . . . i 
Proper stall, tie, and manger i 

Provision for light: Four sq. ft. of 

glass per cow 

Three sq. ft., 3; 2sq. ft.,2; i sq. ft 

I. Deduct for uneven distribution. 

Bedding 

Ventilation 

Provision for fresh air, controllable 

flue system 3 

Windows hinged at bottom, 1.50 

sliding windows i; other openings .50 
Cubic feet of space per cow, 500 feet3 
Less than 500 ft. , 2 ; less than 400 ft. 
i; less than 300 ft., o. 
Provision for controlling tempera- 
ture ] 



UTENSILS 

Construction and condition of utensils 

Water for cleaning 

Clean, convenient and abundant. 

Small-top milking pail 

Milk cooler 

Clean milking suits 



MILK ROOM. OR MILK HOUSE 

Location free from contaminating sur 
roundings 

Construction of milk room 

Floor, walls and ceiling i 

Light, ventilation, screens i 

Separate rooms for washing utensils 
and handling milk 

Facilities for steam Hot water 0.5 . 



Total 



METHODS 



Perfect Allowed 



Clean 

Free from visible dirt 6 



STABLE 

Cleanliness of stable 

Floor 2 

Walls I 

Ceiling and ledges i 

Mangers and partitions i 

Windows I 



Stable air at milking time 

Freedom from dust 3 

Freedom from odors 2 



Cleanliness of bedding 

Barnyard 

Clean i 

Wei! drained I 



Removal of manure daily 

To so feet or more from stable. 



MILK ROOM OR MILK HOUSE 

Cleanliness of milk room 



UTENSILS AND MILKING 

Care and cleanliness of utensils . . . 
Thoroughly washed 2 

Sterilized in steam for 15 minutes. . . .3 
Placed over steam jet or scalded with 

boiling water, 2. 

Protected from contamination 3 

Cleanliness of milking 

Clean, dry hands 3 

Udders washed and wiped 6 

Udders cleaned with moist cloth, 4; 

cleaned with dry cloth or brush at least 

IS minutes before milking, i. 

HANDLING THE MILK 

Cleanliness of attendants in milk room 
MilJ{ removed immediately from stable 

without pouring from pail 

Cooled immediately after milking each 

cow 

Cooled below so° F 

51° to S-S". 4; S6° to 60°, 2. 
Stored below 50° F 

51° to 55°, 2; 56° to 60°, r. 

Transportation below so° F 

51° to 55°. i-So; 56° to 60° I. 

If delivered twice a day allow perfect 
score for storage and transportation. 



Equipment + Methods. 



Final Score 



Note i — If any exceptionally filthy condition is found, particularly dirty utensils, the total score may be 
further limited. 

Note 2 — If the water is exposed to dangerous contamination, or there is evidence of the presence of a dan- 
gerous disease in animals or attendants, the score shall be o. 



SANITARY INSPECTION OF DAIRY FARMS 



MARKET MILK PRODUCTION 



SCORE CARD 

Indorsed by the Official Dairy Instructors' Association. 

( )wner or lessee of farm 

P. O. address State 

'I'otal number of cows Number milking 

C lallons of milk produced daily 

Product is sold by producer to families, hotels, restaurants, stores, 

to dealer 

For milk supply of 

Permit No Date of inspection 191 . . 

Remarks 



{Signed) 

Inspector 

43 



35 

EXERCISE XI 
Judging Dairy Barns 

1. Score according to the official score card, the dairy visited. 
Place the score allowed the different points, on the score card. 

2. On the sheet allotted to notes, write a brief criticism of the 
dairy and the methods employed. Pay particular attention to those 
things which are important in clean milk production, and at the same 
time would not require a big outlay of capital . 



STUDENT'S NOTES AND REPORT 

SCORE 



EQUIPMENT 



Health 

Apparently in good health i 

If tested with tuberculin within a 

year and no tuberculosis is found, 

or if tested within six months and 

all reacting animals removed .... 5 

If tested within a year and reacting 

animals are found and removed 3 

Food clean and wholesome 

Water, clean and fresh 

STABLES 

Location of stable 

Well drained i 

Free from contaminating surround- 
ings 1 

Construction of stable 

Tight, sound floor and proper gutler2 
Smooth, tight walls and ceiling. . . i 
Proper stall, tie, and manger i 

Provision for light: Four sq. ft. ol 

glass per cow 

Three sq. ft., 3; 2sq. ft.,2; i sq. ft., 

I. Deduct for uneven distribution. 

Bedding 

Ventilation 

Provision for fresh air, controllable 

flue system 3 

Windows hinged at bottom, T.50; 

sliding windows i; other openings .50. 
Cubic feet of space per cow, 500 feet3 
Less than 500 ft., 2; less than 400 ft., 
i; less than 300 ft., 0. 
Provision for controlling tempera- 
ture I 



Construction and condition of utensils 

Water for cleaning 

Clean, convenient and abundant. 

Small-top milking pail 

M ilk cooler 

Clean milking suits 

MILK ROOM. OR MILK HOUSE 

Location free from contaminating sur- 
roundings 

Construction of milk room 

Floor, walls and ceiling i 

Light, ventilation, screens i 

Separate rooms for washing utensils 
and handling milk 

Facilities for steam Hot water 0.5 ... . 



SCORE 



Perfect Allowed 



Total 



METHODS 



cows 

Clean 

Free from visible dirt 6 

STABLE 

Cleanliness of stable 

Floor 2 

Walls I 

Ceiling and ledges i 

Mangers and partitions i 

Windows i 

Stable air at milking time 

Freedom from dust 3 

Freedom from odors 2 

Cleanliness of bedding 

Barnyard 

Clean 1 

Well drained i 

'Removal of manure daily 

To so feet or more from stable. 

MILK ROOM OR MILK HOUSE 

Cleanliness of milk room 

UTENSILS AND MILKING 

Care and cleanliness of uten.sils 

Thoroughly washed 2 

Sterilized in steam for is minutes. . . .3 

Placed over steam jet or scalded with 
boiling water, 2. 

Protected from contamination 3 

Cleanliness of milking 

Clean, dry hands ? 

Udders washed and wiped 6 

Udders cleaned with moist cloth, 4; 
cleaned with dry cloth or brush at least 
IS minutes before milking, i. 

HANDLING THE MILK 

Cleanliness of attendants in milk room 
Milk removed immediately from stable 

without pouring from pail 

Cooled immediately after milking each 

cow 

Cooled below 50° F 

51° to S5°. 4; S6° to 60°, 2. 
Stored below so° F 

51° to ss°, 2; s6° to 60°, I. 

Transportation below 50° F 

51° to 55°. I -so; S6° to 60° I. 

If delivered twice a day allow perfect 
score for storage and transportation. 



Perfect Allowed 



Total 



Equipment.. 



Methods. 



Final Score 



Note i — If any exceptionally filthy condition is found, particularly dirty utensils, the total score may be 
further limited. 

Note 1 — If the water is exposed to dangerous contamination, or there is evidence of the presence of a dan- 
gerous disease in animals or attendants, the score shall be 0. 



SANITARY INSPECTION OF DAIRY FARMS 



MARKET MILK PRODUCTION 



SCORE CARD 

Indorsed by the Official Dairy Instructors' Association. 

Owner or lessee of farm 

P. O. address State 

Total number of cows Number milking 

Gallons of milk produced daily 

Product is sold by producer to families, hotels, restaurants, stores, 

to dealer 

For milk supply of 

Permit No Date of inspection 191 

Remarks 



(Signed) 

Inspector 



38 

EXERCISE XII 
Judging Dairy Barns 

1. Score according to the official score card, the dairy visited. 
Place the score allowed the different points, on the score card. 

2. On the sheet allotted to notes, write a brief criticism of the 
dairy and the methods employed. Pay particular attention to those 
things which are important in clean milk production, and at the same 
time would not require a big outlay of capital. 



STUDENT'S NOTES AND REPORT 

SCORE 



EQUIPMENT 



Health 

Apparently in good health i 

If tested with tuberculin within a 

year and no tuberculosis is found, 

or if tested within six months and 

all reacting animals removed . . . . s 

If tested within a year and reacting 

animals are found and removed 3 

Food clean and wholesome 

Water, clean and fresh 

STABLES 

Location of stable 

Well drained 1 

Free from contaminating surround- 
ings I 

Construction of stable 

Tight, sound floor and proper gutter: 
Smooth, tight walls and ceiling. . . . ) 
Proper stall, tie, and manger i 

Provision for light: Four sq. ft. o: 

glass per cow 

Three sq. ft.. 3; 2 sq.ft., 2; I sq. ft. 

I. Deduct for uneven distribution. 

Bedding 

Ventilation 

Provision for fresh air, controUabl 

flue system 

Windoyys hinged at bottom, 1.50 
sliding windows i ; other openings .50 
Cubic feet of space pier cow, 500 feet. 
Less than 500 ft., 2; less than 400 ft.. 
i; less than 300 ft., o. 

Provision for controlling tempera- 
ture 1 



Construction and condition of utensils 

Water for cleaning 

Clean, convenient and abundant. 

Small-top milking pail 

Milk cooler 

Clean milking suits 

MILK ROOM. OR MILK HOUSE 

Location free from contaminating sur- 
roundings 

Construction of milk room 

Floor, walls and ceiling i 

Light, ventilation, screens i 

Separate rooms for washing utensils 
and handling milk 

Facilities for steam Hot water 0.5 ... . 



SCORE 



Perfect Allowed 



Total 



METHODS 



COWS 

Clean 

Free from visible dirt 6 

STABLE 

Clsanliness of stable 

Floor 2 

Walls I 

Ceiling and ledges i 

Mangers and partitions i 

Windows i 

Stable air at milking time 

Freedom from dust 3 

Freedom from odors 2 

Cleanliness of bedding 

Barnyard 

Clean i 

Wei! drained i 

Removal of manure daily 

To so feet or more from stable. 

MILK ROOM OR MILK HOUSE 
Cleanliness of milk room 

UTENSILS AN'D MILKING 

Care and cleanliness of utensils 

Thoroughly washed 2 

Sterilized in steam for 15 minutes. . . .3 
Placed over steam jet or scalded with 

boiling water, 2. 

Protected from contamination 3 

Z^leanliness of milking 

Clean, dry hands 3 

Udders washed and wiped 6 

Udders cleaned with moist cloth, 4; 

:leaned with dry cloth or brush at least 

IS minutes before milking, i. 

HANDLING THE MILK 

Cleanliness of attendants in milk room 
Milk removed immediately from stable 

without pouring from pail 

Cooled immediately after milking each 

cow 

Cooled below so° F 

51° to 55°, 4; S6° to 60°, 2. 
Stored below 50° F 

51° to 55°, 2; 56° to 60°, I. 

Transportation below 50° F 

51° to 55°, i-5o; 56° to 60° I. 

If delivered twice a day allow perfect 
score for storage and transportation. 



Total 



SCORE 



Perfect Allowed 



Equipment + Methods 



Final Score 



Note i — If any exceptionally filthy condition is found, particularly dirty utensils, the total score may be 
further limited. 

Note 2 — If the water is exposed to dangerous contamination, or there is evidence of the presence of a dan- 
gerous disease in animals or attendants, the score shall be 0. 



SANITARY INSPECTION OF DAIRY FARMS 



MARKET MILK PRODUCTION 



SCORE CARD 

Indorsed by the Official Dairy Instructors' Association. 

Owner or lessee of farm 

P. O. address State 

Total number of cows Nimiber milking 

Gallons of milk produced daily ... 

Product is sold by producer to families, hotels, restaurants, stores, 

to dealer 

For milk supply of 

Permit No Date of inspection 191 . . 

Remarks 



{Signed) 

Inspector 



41 

EXERCISE XIII 
Judging City Milk Plant 

1. Judge according to the official score card, a city milk plant. 
Place the scores allowed on the card. 

2. On the sheet allotted to notes, write a brief criticism of the 
plant and the methods employed. Note especially the arrangement 
of the plant as regards convenience for performing work. Also note 
the location and condition of the plant in regard to its sanitary sur- 
roundings. Point out any improvements either in equipment or 
methods which would be beneficial and at the same time require only 
a small outlay of capital. 



STUDENT'S NOTES AND REPORT 
SANITARY INSPECTION OF CITY MILK PLANTS 



Owner or manager Trade name . 

City Street and No State . . . 



Ntmiber of wagons Gallons sold daily 



Milk. 



Cream 



Permit or License No Date of inspection ,191 



EQUIPMENT 



Building: 

Location: Free from contaminating 

surroundings 

Arrangement 

Separate receiving room i 

Separate handling room 2 

Separate wash room i 

Separate sales room i 

Separate boiler room i 

Construction 

Floors tight, sound, cleanable i 

Walls tight, smooth, cleanable . . . . i 
Ceilings smooth, tight, cleanable. . i 

Provision for light i 

Provision for pure air i 

Screens 2 

Minimum of shafting, pulleys, hang- 
ers, exposed pipes, etc i 

Apparatus 

Boiler 2 

Hot-water heater i 

Milk cooler 2 

Refrigerator 2 

Appliances for cleansing utensils and 

bottles 2 

Racks, etc.. for utensils and bottles 

after cleaning i 

Sterilizer for utensils and bottles . . 2 

Bottling and capping machine i 

Wash bowl, soap, and towel for 

attendants 2 

Protection during delivery 2 

Condition of apparatus (make deduc- 
tion for inaccessible parts, open 
seams, rusty ware, decayed or 
battered tables or sink, milk- 
carrying pipes with rough interiois 
and lack of frequent hand coup- 
lings, and for badly worn and 

poorly repaired material) 4 

Laboratory and equipment 

Water supply 

Clean, fresh i 

Convenient and abundant i 



SCORE 



Perfect Allowed 



Total 



METHODS 



Building 

Cleanliness: 

Floors 3 

Walls I 

Ceilings 2 

Doors and windows i 

Shafting, pulleys, hangers, pipes. I 

Freedom from odors 2 

Freedom from flies and other insects 3 
Drainage 2 

Apparatus 

Cleanliness: 

Thoroughly washed and rinsed . . 6 
Sterilized in live steam, thirty 

minutes 5 

(Thoroughly scaled after 
washing with water over 
200° F. or live steam, 3.) 

Bottle caps sterilized 3 

Protected from dirt 2 



H.\ndling milk 

Received below 50° F 5 

(SO°-55°. 4; S5°-6o°, 3.) 

Rapidity of handling in plant 3 

Freedom from undue exposure to air 

in the plant 2 

Capping bottles by machine i 

Bottle top and cap protected by 

covering 2 

Storage 45° F. or below 3 

(4S°-50°, 2; 5o°-SS°, I.) 

Inspection 



Bacteriological work 4 

Inspection of dairies supplying milk 5 
(Once a year, i; twice a year, 2; 

three times a year, 3; four 

times a year, 4.) 

Miscellaneous 



Cleanliness of attendants 2 

(General appearance, hands, etc., 
I ; clean, washable clothing, i.) 
Cleanliness of delivery outfit 2 



SCORE 



Perfect Allowed 



16 



Score for equipment plus score for methods equals Total Score 

Note — If the conditions in any particular are so exceptionally bad as to be inadequately expressed by a 
score of "o" the inspector can make a deduction from the totil score. 



. , Inspector. 



43 

EXERCISE XIV 
Judging City Milk Plant 

1. Judge according to the official score card, a city milk plant. 
Place the scores allowed on the card. 

2. On the sheet allotted to notes, write a brief criticism of the 
plant and the methods employed. Note especially the arrangement 
of the plant as regards conveniences for performing work. Also note 
the location and condition of the plant in regard to its sanitary sur- 
roundings. Point out any improvements either in equipment or 
methods which would be beneficial and at the same time require only 
a small outlay of capital. 



STUDENT'S NOTES AND REPORT 
SANITARY INSPECTION OF CITY MILK PLANTS 



Owner or manager Trade name 

City Street and No State 

Milk 

Cream 

Date of inspection ,191 



Number of wagons Gallons sold daily 

Permit or License No 



EQUIPMENT 



Perfect Allowed 



SCORE 



Building: 

Location: Free from contaminating 

surroundings 

Arrangement 

Separate receiving room i 

Separate handling room 2 

Separate wash room i 

Separate sales room i 

Separate boiler room I 

Construction 

Floors tight, sound, cleanable i 

Walls tight, smooth, cleanable . . . . i 
Ceilings smooth, tight, cleanable. . i 

Provision for light I 

Provision for pure air i 

Screens 2 

Minimum of shafting, pulleys, hang- 
ers, exposed pipes, etc i 

Apparatus 

Boiler 2 

Hot-water heater i 

Milk cooler 2 

Refrigerator 2 

Appliances for cleansing utensils and 

bottles 2 

Racks, etc., for utensils and bottles 

after cleaning i 

Sterilizer for utensils and bottles . . 2 

Bottling and capping machine i 

Wash bowl, soap, and towel for 

attendants 2 

Protection during delivery 2 

Condition of apparatus (make deduc- 
tion for inaccessible parts, open 
seams, rusty ware, decayed or 
battered tables or sink, milk- 
carrying pipes with rough interiors 
and lack of frequent hand coup 
lings, and for badly worn and 

poorly repaired material) 4 

Laboratory and equipment 

Water supply 

Clean, fresh i 

Convenient and abundant i 



Total 



METHODS 



Perfect Allowed 



Building 

Cleanliness: 

Floors 3 

Walls I 

Ceilings 2 

Doors and windows i 

Shafting, pulleys, hangers, pipes, r 

Freedom from odors 2 

Freedom from flies and other insects 3 
Drainage 2 

Apparatus 

Cleanliness: 

Thoroughly washed and rinsed . . 6 
Sterilized in live* steam, thirty 

minutes S 

(Thoroughly scaled after 
washing with water over 
200° F. or live steam, 3.) 

Bottle caps sterilized 3 

Protected from dirt 2 



H.\ndling milk 

Received below 50° F 

(50°-S5°. 4; 55°-6o°, 3.) 

Rapidity of handling in plant 3 

Freedom from undue exposure to air 

in the plant 2 

Capping bottles by machine i 

Bottle top and cap protected by 

covering 2 

Storage 45° F. or below 3 

(45°-50°. 2; SO°-SS°. I.) 

Inspection 



SCORE 



16 



16 



Bacteriological work 4 

Inspection of dairies supplying milk s 
(Once a year, i; twice a year, 2; 

three times a year, 3; four 

times a year, 4.) 

Miscellaneous 



Cleanliness of attendants 2 

(General appearance, hands, etc., 
I ; clean, washable clothing, r.) 
Cleanliness of delivery outfit 2 



Total 



Score for equipmait plus score for methods equals Total Score 

Note — If the conditions in any particular are so exceptionally bad as to be inadequately expressed by a 
score of "o" the inspector can make a deduction from the total score. 



. , Inspector. 



45 

EXPLANATION OF EXERCISES XV AND XVI 

The ability to judge the flavor and odor of milk and cream requires 
considerable practice. There are people whose sense of taste and 
smell is not sufficiently acute to enable them to become good milk and 
cream judges. Persons who have these two senses developed to at 
least a normal degree can, by practice, become very proficient in 
detecting odors and flavors in dairy products. 

The flrst thing to note in judging milk or cream is the visible dirt. 
The sediment found in milk is usually heavier than the other contents 
of the bottle, and therefore sinks to the bottom of the package. The 
dirt is detected by raising the bottle above the eye and noting the 
sediment resting on the bottom. In order to judge milk or cream 
properly, the container should be left undisturbed for at least an hour, 
to give sediment plenty of time to settle. In raising the bottle above 
the eye, great care should be taken not to agitate the contents and so 
drive the dirt into suspension. A reading glass or hand lens is useful 
in aiding one to detect sediment in a bottle of milk or cream. 

The package and seal should be judged before the latter is dis- 
turbed, and before breaking the seal the contents of the bottle shoiild 
be well shaken so that the milk or cream will be thoroughly mixed for 
bacteriological and chemical analysis. Bacteriological examination 
should be made as soon as the package is opened before the milk or 
cream becomes contaminated in any way. In milk and cream con- 
tests, several bottles of the same lot of milk are entered and one of 
these is reserved for bacteriological analysis. 

After judging the package for appearance, the sample is next 
examined for flavor and odor. In judging for flavor and odor it 
is best to warm the sample slightly, as a low temperature disguises 
odors and flavors in milk or cream. 

In order to keep the sense of taste acute it is necessary to rinse out 
the mouth with warm water after tasting each sample. 



46 

EXERCISE XV 
Judging Milk 

I . Judge according to the official score card, the samples of milk 
furnished. If enough score cards are not available, the page allotted 
to notes m^y be ruled off and used to record the scores of the different 
samples. Before beginning the work of this exercise, read carefully 
the directions on the back of the score card and those on page 

Note : — Plating milk for bacteria involves considerable time and 
labor. If it is impossible to plate the samples judged, the bacteria 
score may be called perfect, and the milk judged according to the 
other points on the card. This will not give the true quality of the 
milk, but it will give the student practice in methods of judging which 
is the prime purpose of this exercise. This is particularly true in 
regard to detecting flavors and odors. 



DEPARTMENT OF DAIRY INDUSTRY 



SCORE CARD FOR MILK 



Place 



Class Exhibit No . 



ITEM 



Bacteria 



Flavor and odor 
Visible dirt . . . 
Fat 



Solids net fat 



Acidity- 



Bottle and cap 
Total . . . 



Perfect 
Score 



35 



Score 
Allowed 



Remarks 



Bacteria found per ) 
cubic centimeter / 



Flavor 
Odor . 



Per cent found 



Per cent found 



Per cent found 



i Cap . . 
( Bottle 



Exhibitor 



A ddress . 



Date, 



(Signed) . 

...191 
47 



Judge 



DIRECTIONS FOR SCORING 



BACTERIA PER CUBIC CENTIMETER— PERFECT SCORE, 35 



Points 

Less than 400 35 

400 to 700 34.5 

700 to 1 ,000 34 

1,000 to 2,000 33.5 

2,000 to 3,000 33 

3,000 to 4,000 32. s 

4,000 to 5,000 32 

5,000 to 6,000 31.S 

6,000 to 7,000 31 

7,000 to 8,000 30. s 

8,000 to 9,000 30 

9,000 to 10,000 29 

10,000 to 15,000 28 

15.000 to 20,000 27 

20,000 to 25,000 26 

25,000 to 30,000 25 

30,000 to 35,000. . .*. 24 

35.000 to 40,000 23 

40,000 to 45.000 22 

45,000 to 50,000 21 

50,000 to 55,000 20 

XoTE — When the number of bacteri per cubic centimeter exceeds the local legal limit the 
score shall be o. 

FLAVOR AND ODOR, PERFECT SCORE, 25 

Deductions for disagreeable or foreign odor or flavor should be made according to conditions, 
found. When possible to recognize the cause of the difficulty it should be described under Remarks. 

VISIBLE DIRT— PERFECT SCORE, 10 

Examination for visible dirt should be made only after the milk has stood for some time un- 
disturbed in any way. Raise the bottle carefully in its natural, upright position, without tip- 
ping, until higher than the head. Observe the bottom of the milk with the naked eye or by the 
aid of a reading glass. The presence of the slightest movable speck makes a perfect score im- 
possible. Further deductions should be made according to the amount of dirt found. When 
possible the nature of the dirt should be described under Remarks. 



Points 

55,000 to 60,000 19. 

60,000 to 65,000 18 

65,000 to 70,000 17 

70,000 to 75,000 16 

75,000 to 80,000 15 

80,000 to 85,000 14 

85,000 to 90,000 13 

90,000 to 95.000 12 

95,000 to 100,000 II 

100,000 to 1 10,000 10 

I 10.000 to 120,000 9 

120,000 to 130,000 8 

130,000 to 140,000 7 

140,000 to 150,000 6 

150,000 to 160,000 5 

160,000 to 170,000 4 

170,000 to 180,000 3. 

180,000 to 190,000 2 

190,000 to 200,000 I 

200,000 and over o 



FAT IN MILK— PERFECT SCORE, 10 



Points 
4.0 per cent and over lo 



Points 



9 per cent 9.8 

8 per cent 9.6 

7 per cent 9.4 

6 per cent 9.2 

5 per cent 9 

Note — New York State legal limit, 3% fat. 



3.4 per cent. 
3.3 per cent 
3.2 per cent 
3.1 per cent. 
3.0 per cent. 



SOLIDS NOT FAT— PERFECT SCORE, 10 



Points 

3.7 per cent and over 10 

3.6 per cent 9 

3.5 per cent 8 

3.4 per cent 7 

3.3 per cent 

3.2 per cent 5 



8.1 per cent 

8.0 per cent 

7.9 per cent 

7.8 per cent 

Less than 7.8 per cent . 



Points 
4 



New York State legal limit, 11.5% total solids. 



ACIDITY— PERFECT SCORE. 5 



Less than 0.2 per cent 

0.2 per cent to 0.21 per cent. . 
0.21 per cent to 0.22 per cent. 



Points 
5 
4 
3 



Points 



0.22 per cent to 0.23 per cent. 
0.23 per cent to 0.24 per cent . 
0.24 per cent and over 



BOTTLE AND CAP— PERFECT SCORE, 5 

Bottles should be made of clear glass and free from attached metal parts. Caps should b& 
sealed in their place with hot paraffin, or both cap and top of bottle covered with parchment 
paper or other protection against water and dirt. Deduct for tinted glass, attached metal parts, 
unprotected or leaky caps, partially filled bottles, or other conditions permitting contaminatioa 
of milk or detracting from the appearance of the package. 



49 

EXERCISE XVI 
Judging Cream 

I . Judge according to the official score card, the samples of cream 
furnished. If enough score cards are not available, the page allotted 
to notes may be ruled off and used to record the scores of the different 
samples. Before beginning the work of this exercise, read carefully 
the directions on the back of the score card and those on page. 

Note : — Plating milk for bacteria involves considerable time and 
labor. If it is impossible to plate the samples judged, the bacteria 
score may be called perfect and the milk judged according to the 
other points on the card. This will not give the true quality of the 
milk, but it will give the student practice in methods of judging which 
is the prime purpose of this exercise. This is particularly true in 
regard to detecting flavors and odors. 



SCORE CARD FOR MILK 



Place 



Class Exhibit No . 



ITEM 


Perfect 
Score 


Score 
Allowed 


Remarks 




35 
25 
10 
20 

5 
5 




Bacteria found per \ 


Bacteria 


cubic centimeter J 
( Flavor 


Flavor and odor . . 




Visible dirt 




( Odor 


Fat 




Per cent found 


Acidity 




Per cent found 


Bottle and cap 




(Cap 


Total 


100 




( Bottle 









Exhibitor 



Address. 



(Signed) . 



Judge 



Date, 



..191 
50 



EXPLANATION OF SCORES 



BACTERU PER CUBIC CENTIMETER— PERFECT SCORE, 35 



Points 

Less than 400 35 

400 and less than 700 34.5 

700 and less than 1,000 34 

1,000 and less than 2,000 33.5 

2,000 and less than 3,000 33 

3,000 and less than 4,000 32.5 

4,000 and less than 5,000 32 

5,000 and less than 6,000 31. S 

6,000 and less than 7,000 31 

7,000 and less than 8,000 30.5 

8,000 and less than 9,000 30 

9,000 and less than 10,000 29 

10,000 and less than 15,000 28 

15,000 and less than 20,000 27 

20,000 and less than 25,000 26 

25,000 and less than 30,000 25 

30,000 and less than 35,000 24 

35,000 and less than 40,000 23 

40,000 and less than 45,000 22 

45,000 and less than 50,000 21 

50,000 and less than 55,000 20 



Points 

55,000 and less than 60,000 ig 

60,000 and less than 65,000 18 

65,000 and less than 70,000 17 

70,000 and less than 75,000 16 

75,000 and less than 80,000 15 

80,000 and less than 85,000 14 

85,000 and less than 90,000 13 

90,000 and less than 95,000 12 

95,000 and lass than 100,000 11 

100,000 and less than 110,000 10 

110,000 and less than 120,000 9 

120,000 and less than 130,000 8 

130,000 and less than 140,000 7 

140,000 and less than 150,000 6 

150,000 and less than 160,000 5 

160,000 and less than 170,000 4 

170,000 and less than 180,000 3 

180,000 and less than 190,000 2 

190,000 and less than 200,000 i 

200,000 and over o 



FLAVOR AND ODOR, PERFECT SCORE, 25 

Deductions for disagreeable or foreign odor or flavor are made according to conditions 
found. When possible to recognize the cause of the difficulty it is described under Remarks. 

VISIBLE DIRT— PERFECT SCORE, 10 

Examination for visible dirt is made only after the milk has stood for some time un- 
disturbed in any way. Raise the bottle carefully in its natural, upright position, without tip- 
ping, until higher than the head. Observe the bottom of the milk with the naked eye or by the 
aid of a reading glass. The presence of the slightest movable speck makes a perfect score im- 
possible. Further deductions are made according to the amount of dirt found. When possible 
the nature of the dirt is described under Remarks. 

FAT IN CREAM— PERFECT SCORE, 20 

If 20 per cent fat or above, score perfect. Deduct i point for each one-half per cent 
fat below 20. 

ACIDITY— PERFECT SCORE, 5 



0.2 per cent or less 

0.21 per cent or over 0.20. 
0.22 per cent or over 0.21 . 



Points 
5 
4 
3 



0.23 per cent or over 0.22 . 
0.24 per cent or over 0.23 . 
Over 0.24 per cent 



Points 



BOTTLE AND CAP— PERFECT SCORE, 5 

Bottles should be made of clear glass and free from attached metal parts. Caps should be 
sealed in their place with hot paraffin, or both cap and top of bottle covered with parchment 
paper or other protection against water and dirt. Deductions are made for tinted glass, attached 
metal parts, unprotected or leaky caps, partially filled bottles, or other conditions permitting 
contamination of milk or detracting from the appearance of the package. 



51 



52 

EXPLANATION OF EXERCISE XVII 

The main purpose of a bottle filler is to fill several bottles at the 
same time and to do it in such a manner that there will be the smallest 
possible amount of loss. With the modern filler the overflow, air, 
froth, etc., is removed from the bottle by means of a small tube which 
connects with the filler tube and extends upward above the level of the 
milk in the filler tank. In cleaning the machine it is necesslary to 
scrub the inside of these tubes with a long handled brush provided for 
the purpose. Simply rinsing the tube is not sufficient. The filler 
tubes usually consist of two parts, one which fits over the other, and 
the outside tube works up and down on the inside tube when the filler 
is operated. This makes it necessary for the tubes to fit perfectly, 
and great care must be taken not to roughen the surfaces of these 
tubes. In some cases the outside and inside tubes are numbered to 
correspond so that the operator in assembling the machine may 
always know which tubes fit one another. 

The end of the outside filler tube is provided with a rubber gasket 
so that a perfect union is made with the bottle when the filler is in 
operation. Bottles with chipped and broken edges are liable to cut 
the rubber gaskets, and unless pains are taken to clean them they 
become filled with milk, rendering them unsanitary. 

Bottles to be washed, should first be soaked in water as hot as the 
hand will bear, to which has been added some washing powder. After 
washing on the brushes, the bottles should be rinsed in a tank of clean, 
hot water. The bottles should then be steriHzed by means of live 
steam. If live steam is not available they may be placed in scalding 
hot water. It is best not to place the crates used to fill bottles inside 
the sterilizer, as the action of live steam soon destroys the crates. 
Crates suitable for this purpose may be made from ordinary lumber. 
This method, however, has the disadvantage of making it necessary to 
transfer the bottles to the filler crates at the time of bottling. 



S3 

EXERCISE XVII 
Bottling Milk and Washing Bottles 

1. Place all loose parts of the filler in the filler tank and scald 
them with hot water. Note whether the outside and inside filler 
tubes are numbered and if they are, be sure to place together those 
bearing the same number. Fill two cases of quart and one case of 
pint bottles. Cap one case of quarts with the standard cap. Ice this 
crate of bottles and set in the refrigerator. Fill one case of Dacro 
bottles (small topped) and cap them. 

2. Remove the old milk from the refrigerator and pour the milk 
into a can. Also empty all bottles of milk not iced, and draw off into 
a can all milk in the fillers. Wash the fillers, using small brushes for 
the tubes. Collect all dirty bottles and wash them. Wash the 
Dacro bottles with the foot power washer. Place the washed bottles 
in the sterilizer and turn on the steam before leaving. 



54 
STUDENT'S NOTES AND REPORT 



55 

EXPLANATION OF EXERCISE XVIII 

The clarification of milk consists in removing from it the insoluble 
dirt. The modern clarifier does this by means of centrifugal force. 
The dirt found in milk is usually heavier than the milk itself and the 
action of the centrifugal force deposits this dirt on the inside of the 
bowl. Clarifiers work on much the same principle as do separators, 
but each make of machine has special features tending to prevent 
separation. Usually a clarifier runs slower than does a separator of 
the same make and capacity. In a separator, the inner device is so 
constructed as to spread the milk in a thin layer, thereby making it 
possible to do more complete separation. 

In a clarifier the milk is not separated in as thin a layer and only 
one outlet to the bowl is provided. 

The different construction of each machine will be studied when 
the machine is used. 

EXERCISE XVIII 
Effect of Temperature on Clarification 

1. Weigh out two cans of milk and thoroughly mix them by 
pouring from one can to another until they are of uniform composi- 
tion. 

2 . Clarify one can of milk at a temperature of 60° F. and clarify 
the other at a temperatiu-e of 85° F. Note if there is any difference 
in the kind and amount of sediment obtained. 

3. Stain some of the sediment obtained from each clarification 
and make a drawing of the field. In case there is no microscopical 
difference in the sediment only one drawing need be made. 



56 
STUDENT'S NOTES AND REPORT 



57 

EXERCISE XIX 

1. For use with the clarifier, weigh a can of milk and have the 
temperattire as near 60° F. as possible. Measure out 100 cc. of the 
milk into a measuring cylinder, both before and after clarification. 
Set these two cylinders aside and the next day compare the cream line 
on the two samples. Also note if there is any sediment in the bottom 
of either cylinder, and if so compare the amount. 

2. Run the milk through the clarifier and keep track of the time 
required for the process. Note the kind and amount of sediment 
on the inside of the bowl. 

3. Stain some of the sediment on a glass slide and examine it 
under the high power microscope. Make a drawing of the field. 

4. Reclarify the same amount of milk and compare the amount 
and kind of sediment with that obtained in the first clarification. 

5. Make a drawing showing the difference between the inner 
device in a separator and a clarifier of the same make. 



58 
STUDENT'S NOTES AND REPORT 



59 

EXPLANATION OF EXERCISE XX 

In sanitary milk production it must be kept constantly in mind 
that clean milk means a product reasonably free from germ life. It 
is not as difficult to keep germs out of milk as is commonly supposed. 
There are a few simple and inexpensive practices which if carefully 
followed will do much in aiding the dairyman to produce a good 
product. 

It is the purpose of the following experiments to illustrate the value 
of certain dairy practices in clean milk production and the harmful 
effects of certain other practices in producing clean milk. 

In performing these experiments it must be borne in mind that 
anything which prevents the entrance of dust and dirt into milk 
is an aid to clean milk production. On the other hand, any disturb- 
ance which causes dust particles to float around in the air makes it 
easily possible for these particles to enter the milk while it is being 
drawn and so contaminate it. 

The use of the small top pail, and wiping the udder with a damp 
cloth just before milking, are two things which are easy to do and are 
comparatively inexpensive. At the same time, they are exceedingly 
helpful in keeping germs out of milk. 

On the other hand, the practice of feeding hay or grain just before 
milking stirs up a dust and therefore makes it possible for a larger 
ntunber of micro-organisms to enter the milk. 



EXERCISE XX 
The Value of the Small Top Pail in Clean Milk Production 

1 . Careftdly sterilize an ordinary wide top milk pail and a small 
top or covered milk pail. 

2. Select two cows standing near one another and whose flanks 
and udders are alike as regards the amount of visible dirt on them. 
Milk one cow in the wide mouth pail and the other cow in the small 
top or covered pail. 

3. Take a sample of milk in a sterile bottle from each pail and 
plate the samples for bacteria. If it is necessary to hold the samples 
for any length of time before plating, the bottle should be set on ice. 

4. After the colonies in the plates have developed, note if there 
is any difference in bacterial content of the milk drawn in the wide 
mouth pail and that drawn in the small top or covered pail. 



6o 
STUDENT'S NOTES AND REPORT 



6 1 

EXERCISE XXI 

Effect of Dampening Udder and Flank on Germ Content of 

Milk 

1. Carefully sterilize two small top or covered pails. 

2. Select two cows standing near one another whose udders and 
flanks are alike so far as amount of visible dirt is concerned. 

3. Dampen with a cloth the udder and flanks of one of the cows 
and milk her. 

4. Milk the other cow without dampening the flank and udder. 

5. In a sterile bottle, take a sample of milk from each milking and 
plate the milk for bacteria. If the milk cannot be plated at once, the 
bottle should be kept on ice. Compare the ntimber of bacteria found 
in the milk drawn under the two different conditions. 



62 

STUDENT'S NOTES AND REPORT 



63 

EXERCISE XXII 

Effect of Feeding Hay, Just Before Milking, on the Germ 

Content of Milk 

1 . Sterilize two small top pails and select two cows whose udders 
and flanks are alike as regards the amount of visible dirt on them. 

2 . Milk one of the cows and take in a sterile bottle a sample of the 
milk for plating. 

3 . Before milking the second cow, shake two or three forkfuls of 
hay near where she stands. Milk the cow and take in a sterile bottle 
a sample of the milk for plating. 

4. Compare the nimiber of bacteria found in the milk drawn 
before and after the hay was shaken. 



64 
STUDENT'S NOTES AND REPORT 



INDEX 

Bottle fillers 52 

Bottling milk 53 

Bottle washing 53 

Clarification of milk 55. 57 

Clarifier 55 

Cooling Milk 21,25 

in cans 21 

with brine and ice 26,27 

with conical cooler 23 

Dairy Utensils 6 

Cleaning of 5 

Construction of 6 

Damp Cloth 59. 61 

Use in clean milk production 61 

Dust 59 

Effect of in clean milk production 59 

Milk 

Bottling 53 

Clean 5 

Cooling of milk 21,25 

Judging of 45 , 46, 47 

Standardizing 8, 13 

Pasteurization 16 

Flash method 19 

Holder method 17 

Salt : 26 

Use of in cooling milk 26, 27 

Score Card 31 

for city milk plants 41 

for cream 49 

for Dairy building 32 

for milk 45 

Small ^"op pail 59 

Efficiency of 59 

Standardization 8,13 

Temperature 21 

of milk for clarification 55 



6S 



: J^^^' 'II': 




